Mascarenhas has signed a two-year contract and will visit Dunedin in the next fortnight to finalise some details.
The 36-year-old has an extensive playing background, including two stints with the Volts.
He made 34 appearances for England in limited-overs fixtures and enjoyed a long first-class career (18 years) in which he built a reputation as a wily medium pacer and hard-hitting lower-order batsman.
His coaching resume is brief by comparison but Otago Cricket Association chief executive Ross Dykes said Mascarenhas' ''tactical awareness and his ability to build relationships set him apart'' from the other candidates.
''He has a great depth of experience in cricket at a high level and also has knowledge of Otago cricket,'' Dykes said.
''So we didn't have to worry about someone new coming in and not knowing the setup and not knowing what we have available to us.
''He also has such a strong reputation as a people's person and someone who can engage players and who has such a positive outlook on the game.''
Mascarenhas has been a bowling coach for Hampshire and several IPL teams and, more recently, he has been involved as a player and an assistant coach with the Hobart Hurricanes.
Dykes said he had some excellent references regarding his coaching work but it was his ''depth of knowledge and ability to read a game which was the defining influence''.
Mascarenhas has playing commitments with the Hobart Hurricanes at the Champions League in September but plans to retire as a player after that.
''Being the assistant coach for the Hobart Hurricanes last season gave me a bit of a grounding and a bit of insight into what it takes as well,'' Mascarenhas said.
''Obviously, I'm coming into a very successful team. So it is a big challenge to keep that going and keep winning trophies.
''I've been there as a player so I did learn a bit about the culture and what is involved around the Otago setup.
''Hopefully, I'll be able to bring some new insights without changing the culture too much.''
As a bowler, Mascarenhas used swing and guile rather than pace and bounce to trap his victims.
He worked hard at his craft and hopes that experience will be of a benefit to the likes of young Otago bowlers Jacob Duffy and Blair Soper.
''There are not too many first-class cricketers around the traps who bowl the same pace as I do. Just from that point of view, to be successful as a bowler, I really had to work hard and gained a lot of experience and know-how of how to bowl, is the way that I put it.''
Mascarenhas married Nadine in 2011. The couple, who live in Melbourne, have a 2-year-old son, Lenny, and Nadine is pregnant with a due date in July.
''I will come over before but we have not actually finalised a [start] date to get things under way for the preseason. But obviously I have to go off to the Champions League and then come straight back. Once I come back, the family will move over then.''
